1. Field of the Invention
This invention pertains to transporting objects, and more particularly to apparatus for orienting workpieces and propelling them along selected paths.
2. Description of the Prior Art
It is well known to transport workpieces along elongated paths between work stations located along the paths. A rather specialized application of workpiece transporting equipment involves conveyors, such as roller conveyors, that support either the workpieces or workpiece carrying pallets. Examples of prior conveyors for propelling workpieces may be seen in U.S. Pat. Nos. 3,716,129; 3,810,538; 3,960,262; 4,108,303; 4,109,783; 4,174,777; 4,227,607; 4,240,538; and 4,817,784.
Change of direction of a workpiece along a conveyor path may generally be accomplished in one of four ways. First, the conveyor may be constructed with a rather large radius corner, such as is shown in U.S. Pat. No. 4,096,942. That construction enables a pallet to change direction with minimum expense or complexity.
It is also possible to use turntable corners for changing the direction of a workpiece on a conveyor. Turntable corners have the advantage of occupying less space than large radius corners. In addition, turntable corners can be used to change the orientation of a workpiece without necessarily changing its translational direction along a path. Turntable corners are also capable of diverting a workpiece or pallet from one path to an intersecting path. For example, turntable corners can rotate 90 degrees and transfer a workpiece to a branch path. Turntable corners are also capable of rotating 180 degrees and continuing to propel the workpiece in the initial direction. Additionally, turntable corners can merely propel a workpiece downstream without imparting any rotary motion to it. U.S. Pat. No. 3,530,571 shows a conveyor system with multiple paths and turntable corners at the junctions of various paths. U.S. Pat. No. 5,086,910 describes an exemplary conveyor system that includes both large radius corners and turntable corners.
Another mechanism that reorients and redirects workpieces along a conveyor path is a lift and rotate mechanism. Those mechanisms lift a workpiece, rotate it, and then lower it back to the plane of the conveyor. A lift and rotate mechanism is required if a 90 degree change in workpiece orientation relative to its direction of travel is required. Such lift and rotate mechanisms are large and sturdily built in order to handle heavy workpieces. In particular, their bearings must be adequate to handle heavy weights. They are also quite complicated because the lifting plates must clear their propelling rollers. Because of their size and weight, it is quite difficult to operate them manually if a failure of the turntable mechanism occurs. A closely related disadvantage of lift and rotate devices is their high cost of construction and maintenance.
Another prior device for changing the direction of a workpiece along a path is a lift and transfer mechanism. A lift and transfer mechanism lifts the workpiece from one conveyor path and then transfers it to a branch path that is at a higher elevation. Like the lift and rotate mechanisms, lift and transfer mechanisms must be large, expensive, and complicated in order to handle heavy workpieces. If a failure should occur, the lift and transfer function is very difficult to perform manually.
It is therefore highly desirable to develop an improved turning corner for workpiece handling conveyor systems.